A chart is a graphical representation of numerical data. Charts are particularly useful for presenting complicated data in a concise and easily-understandable form. In today's desktop publishing environment, users can create impressive presentations using charts. Charts are based on underlying data that is entered into an application program such as “EXCEL” from MICROSOFT CORPORATION. The underlying data can then be used to create a chart of the data in a number of different formats, such as pie-chart, bar-chart, histogram, line chart, etc. In addition, each part of the chart can have associated colors, textures, and other effects to improve the appearance of the chart, which is very important for conveying information.
Application programs have traditionally used primitive function calls to render charts. The graphics display interface (GDI or GDI+) from “MICROSOFT WINDOWS” and GEL from “MICROSOFT OFFICE”, for example, are relatively low-level interfaces that are often used by application programs to render charts. Such low-level interfaces typically provide functions for rendering chart elements at a pixel level. For example, to draw a line, an application program must specify a beginning pixel and an ending pixel. Later, if the line were being stretched, the application program must again specify the new beginning and/or ending pixel. The traditional interfaces do not include higher-level functions, such as a line-stretching function, for handling a group of pixels as a line.
Another problem is that different application programs have traditionally rendered charts differently. For example, in “MICROSOFT WINDOWS”, one application program may use the GDI, while another application may use a combination of calls to GEL and GDI. Because the charts are rendered differently, similar elements in charts rendered by different application programs may appear different to the user. Thus, a chart that should otherwise appear the same in MICROSOFT “POWERPOINT” and “EXCEL”, for example, may appear slightly different in the two application programs.
Users often copy a chart from one application program and import it into another application program. For example, a chart can be copied from “EXCEL” and pasted into a MICROSOFT “WORD” document or a “POWERPOINT” presentation. Traditionally, a user has been able to paste the chart as either a chart object or a picture. Unfortunately, when the user pastes the chart as a picture, the chart is severed from the underlying data that was used to create the picture. This means the user can no longer manipulate the underlying data of the chart through the pasted chart. For example, the user cannot edit the numerical data or labels in the chart once the chart is pasted as a picture.
In addition, when they are not pasted as pictures, charts in documents can have certain drawbacks. These drawbacks are primarily due to the fact that the chart that is not in picture format is not generated with presentation aspects in mind. For example, sometimes charts appear with an aliasing effect that is distracting to the eye. As another example, when the user resizes the chart, text can appear unusual because the font scaling is imprecise. As yet another example, the chart that is not pasted as a picture sometimes appears different on the computer screen as it does in a printout, because of a difference in coordinate mapping.
Thus, there is a need for the ability to render and manipulate charts consistently across applications. In addition, there is a need to provide a consistent, high-quality presentation of charts while enabling users to manipulate underlying elements of the chart.